The waistband of my trousers confirms that there has been no commensurate loss of flesh.
However, I now need to establish exactly what my weight is. It makes some sense that the accuracy of my scales deteriorated as the batteries became exhausted. Looking at the recorded weights of the last two years (all on that same set of batteries), it remained fairly consistently between 83-88 kg, with the variations depending on how seriously I took being overweight. At 88kg, my recorded waist measurement was exactly what it is now. From the beginning of lockdown I have not worked, so I have not visited restaurants or been involved in big social get togethers, I've done more exercise than usual and even been fairly seriously ill, yet my weight (according to Garmin) increased from 87kg to 96kg. yet my clothes fit as they always did. The newly-rebatteried scale gave me a weight of 86.6kg. Hitherto, I would have regarded that as reasonable (FACVO reasonable...) whereas 96kg worried me enough to take on Dry January and the Tour de Zwift - neither of which apparently reduced my weight one iota.
Given that my gym remains shut, and I will not trouble my GP for the triviality of checking my weight, I may have to buy a set of scales simply as a double-check!